According to the National Institute of Standards and Technology (NIST) — which is the U.S. government agency that investigated the World Trade Center’s destruction — the Twin Towers came down “essentially in free fall.” 1

NIST’s theory of the collapses hinges on the idea that the upper section of each tower could continuously accelerate through the lower stories at nearly the rate of gravity, while in the process completely dismembering the steel frames and pulverizing nearly all of the concrete to a fine powder.

Yet NIST provided no modeling or calculations to demonstrate that such behavior was possible. Instead, NIST arbitrarily stopped its analysis at the moment of “collapse initiation,” asserting that total collapse was “inevitable” once the collapses initiated.2

Astonishingly, NIST’s entire explanation for why the lower sections failed to stop or even slow the descent of the upper sections is limited to half a page of its 10,000-page report, in a section titled “Events Following Collapse Initiation,” 3 which asserts:

“The structure below the level of collapse initiation provided minimal resistance to the falling building mass at and above the impact zone. The potential energy released by the downward movement of the large building mass far exceeded the capacity of the intact structure below to absorb that through energy of deformation. 

“Since the stories below the level of collapse initiation provided little resistance to the tremendous energy released by the falling building mass, the building section above came down essentially in free fall, as seen in videos.” — p. 146, NIST NCSTAR 1

In 2007, a group of scientists, an architect, and two 9/11 family members filed a “Request for Correction” to the NIST report under the Information Quality Act. They argued that, among other things, NIST failed to establish the likely technical cause of the building failures because it did not explain why, after collapse initiation, total collapse had ensued.4 They wrote:

“Here, NIST has not offered any explanation as to why (i.e. the technical cause of) the story below the collapse zone was not able to arrest the downward movement of the upper floors. The statement “as evidenced by the videos from several vantage points” is only an explanation of what occurred, but gives the reader absolutely no idea why it occurred. Basic principles of engineering (for example, the conservation of momentum principle) would dictate that the undamaged steel structure below the collapse zone would, at the very least, resist and slow the downward movement of the stories above…. The families of the firefighters and WTC employees that were trapped in the stairwells when the entirety of the WTC Towers collapsed on top of them would surely appreciate an adequate explanation of why the lower structure failed to arrest or even resist the collapse of the upper floors.” — p. 20, Request for Correction

NIST responded to the Request for Correction with the remarkable admission that it was not able to provide a full explanation of the total collapse: 5

“NIST carried its analysis to the point where the buildings reached global instability. At this point, because of the magnitude of deflections and the number of failures occurring, the computer models are not able to converge on a solution…. [W]e are unable to provide a full explanation of the total collapse.” — p. 3-4, NIST Response to Request for Correction

Total Collapse Explained

While NIST failed to provide an explanation for the total collapse of the Twin Towers, several independent researchers have taken on that challenge.

The upper section of the North Tower.

Central to their analysis has been to measure the downward motion of the upper section of WTC 1 (the North Tower). Two papers in particular have found that, in the four seconds before the upper section disappeared from view, the rate of acceleration remained constant, at approximately 64 percent of free fall,6 and there was never an observable deceleration.7

Based on Newton’s Third Law of Motion, which states that for every action there is an equal and opposite reaction, we know there would have been a deceleration of WTC 1’s upper section if it had impacted and crushed the intact structure below it. The absence of deceleration is incontrovertible proof that another force (i.e., explosives) must have been responsible for destroying the lower structure before the upper section reached it.

Figure 1: This graph from David Chandler’s “Destruction of the World Trade Center North Tower and Fundamental Physics” (Journal of 9/11 Studies, February 2010) shows that the North Tower’s upper section traveled at nearly uniform downward acceleration of -6.31 m/s2 (with an R2 value of 0.997), or 64% of free fall.

In 2011, the ASCE’s Journal of Engineering Mechanics published a paper by Dr. Zdeněk Bažant and Jia-Liang Le titled “Why the Observed Motion History of the World Trade Center Towers Is Smooth,” 8 in which the authors attempted to argue that the upper section’s deceleration was “far too small to be perceptible,” thus accounting for why the observed motion is “smooth.” Specifically, they calculated, the deceleration was “three orders of magnitudes smaller than the error of an amateur video, and thus undetectable.”

In response, researchers Tony Szamboti and Richard Johns submitted a Discussion paper to the Journal of Engineering Mechanics in May 2011.9 Their paper argued that Bažant and Le had used incorrect values for (1) the resistance of the columns, (2) the lower structure’s floor mass, and (3) the upper section’s total mass. Szamboti and Johns showed that when the correct values are applied, Bažant and Le’s analysis actually proves that the deceleration of the upper section would have been significant and detectable (if it were a true fire-induced progressive collapse), and that the collapse would have arrested within three seconds.

Unfortunately, the Journal of Engineering Mechanics inexplicably rejected Szamboti and Johns’ Discussion paper as “out of scope” after holding it in review for 27 months. So Szamboti and Johns, along with Dr. Gregory Szuladziński, a world-renowned expert in structural mechanics, wrote another paper refuting Bažant and Le’s analysis and submitted it to the International Journal of Protective Structures. That paper, titled “Some Misunderstandings Related to the WTC Collapse Analysis,” 10 was published in June 2013.

So little research has been published on why the Twin Towers underwent total collapse that Bažant and Le’s 2011 paper, and Bažant’s three earlier papers on the subject, are the only analysis that exists to support the official explanation of a fire-induced progressive collapse. That analysis has now been indisputably debunked by Szamboti, Johns, Szuladziński, and others.


Endnotes

[1] NIST: Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Towers (December 1, 2005), p.146. (NIST NCSTAR 1)

[2] NIST NCSTAR 1, p.xxxvii, p. 82.

[3] NIST NCSTAR 1, p.146.

[4] McIlvaine, Bob et al. “9/11 Family Members and Scholars: Request for Correction Submitted to NIST,” Journal of 9/11 Studies (June 2007).

[5] NIST: Response to the Request for Correction (September 2007). 

[6] Chandler, David: “The Destruction of the World Trade Center North Tower and Fundamental Physics,” Journal of 9/11 Studies (February 2010).

[7] Szamboti, Tony and MacQueen, Graeme: “The Missing Jolt: A Simple Refutation of the NIST-Bazant Collapse Hypothesis,” Journal of 9/11 Studies (April 2009).

[8] Bažant, Zdeněk and Le, Jia-Liang: “Why the Observed Motion History of the World Trade Center Towers is Smooth,” Journal of Engineering Mechanics (January 2011).

[9] Szamboti, Tony and Johns, Richard: “ASCE Journals Refuse to Correct Fraudulent Paper Published on WTC Collapses,” Journal of 9/11 Studies (September 2014).

[10] Szuladziński, Gregory and Szamboti, Tony and Johns, Richard: “Some Misunderstandings Related to WTC Collapse Analysis,” International Journal of Protective Structures (June 2013). 

The report issued by the National Institute of Standards and Technology (NIST) on the destruction of WTC 1 and WTC 2 was voluminous, yet NIST did not analyze what is arguably the most important aspect of the collapses for establishing their likely technical cause: the structural behavior of the towers during the collapse. Instead, NIST carried its analysis only to the point of what it called “collapse initiation.”

As a result of stopping its analysis at collapse initiation, NIST’s final report provides virtually no explanation for the most relevant body of evidence. The very limited explanations NIST does provide come mainly from its FAQs webpage and are speculative rather than based upon scientific analysis.

Pulverization and Dismemberment

One of the most noticeable features of the Twin Towers’ destruction was the near-total pulverization of their concrete flooring. New York Governor George Pataki provided this account:

“There’s no concrete. There’s very little concrete. All you see is aluminum and steel. The concrete was pulverized. And I was down here on Tuesday, and it was like you were on a foreign planet. All over lower Manhattan — not just this site — from river to river, there was dust, powder two, three inches thick. The concrete was just pulverized.”

Pulverized concrete submerged lower Manhattan in enormous dust clouds and blanketed the streets with several inches of dust.

In addition, the buildings’ steel structures were almost entirely dismembered. Aside from some of the exterior walls at the base of each building still standing, virtually all of their steel skeletons were broken up into small pieces, with the core structures separated into individual members and the exterior columns broken up into three-story, prefabricated sections.

Debris from the dismembered structures of WTC 1 and WTC 2.

What can explain the near-total pulverization of approximately 8.8 million square feet of 5.5-inch-thick lightweight concrete flooring and the near-total dismemberment of 220 stories of steel structure? NIST provides no explanation, and gravity alone appears to be implausible. A simple analysis of the approximate amount of energy required to pulverize the concrete and dismember the steel structures indicates that about 1,255 gigajoules of energy would have been required, far exceeding the estimated 508 gigajoules of gravitational potential energy contained in the buildings.1

The near-total pulverization and dismemberment of the structures becomes even more difficult to explain when we consider that the collapses occurred “essentially in free fall.”2 Near-total pulverization and dismemberment would require a tremendous collision of materials at each floor, and yet NIST claims that the structure below “offered minimal resistance to the falling building mass.”3 The official hypothesis thus attempts to have it both ways: “minimal resistance,” “free fall,” deceleration “far too small to be perceptible”4 — and yet near-total pulverization and dismemberment of the buildings’ concrete and steel. But according to Dr. Steven Jones, a former physics professor at Brigham Young University, “The paradox is easily resolved by the explosive demolition hypothesis, whereby explosives quickly remove lower-floor material including steel support columns and allow near free-fall-speed collapses.”5

Explosive Ejection of Materials

As the concrete was being pulverized and the structures were being dismembered, a large percentage of the buildings’ materials was ejected laterally far beyond the perimeters of the buildings. According to the FEMA Building Performance Study, the debris fields extended as far as 400 to 500 feet from each tower’s base.

The materials of WTC 1, including multi-ton beams, were explosively ejected several hundred feet in all directions.

In the popular five-minute video titled North Tower Exploding, produced by physics teacher David Chandler, he describes the observed explosive ejection of materials from WTC 1:

“[U]nder the canopy of falling debris, do you see the rapid sequence of explosive ejections of material? Some of the jets have been clocked at over 100 mph.... They’re continuous and widespread. They move progressively down the faces of the building, keeping pace with the falling debris.... The building is being progressively destroyed from the top down by waves of explosions creating a huge debris field.”

Chandler then describes the hurling of multi-ton steel members:

“Notice that embedded in the dust clouds are huge girders and entire sections of steel framing that are being hurled out of the building.... Some landed as much as two football fields away from the base of the tower.”

Chandler next addresses the claim that the ejection of these girders was caused by a spring action resulting from the upper sections crushing down upon them.

“Some people have suggested that the weight of the tower crushing down on the girders caused them to flex and they sprung sideways by a spring action. But we are not seeing isolated jumping girders. We are seeing a major fraction of the mass of the building...reduced to small pieces of rubble and fine dust, and being explosively ejected in all directions.”

Demolition Squibs

Along with the pulverization, dismemberment, and explosive ejection of the buildings’ materials, we observed what Kevin Ryan describes as “high velocity bursts of debris ejected from point-like sources.”6 According to Ryan, “[T]he demolition hypothesis suggests that these bursts of debris are the result of the detonation of explosive charges (squibs), placed at key points in the structure to facilitate the removal of resistance.” Ryan goes on to describe these apparent squibs in more detail:

High-velocity bursts of debris, or “squibs,” were ejected from point-like sources in WTC 1 and WTC 2, as many as 20 to 30 stories below the collapse front.

“In the videos we can see these bursts being ejected from the sides of the towers nearly 30 floors below the collapse front....

“Each of these was a sharp emission that appeared to come from a point-like source, ejecting approximately 50 to 100 feet from the side of the building in a fraction of a second. From the extracted frames of the KTLA video,16 we can estimate that one of the bursts was fully ejected in approximately .45 seconds. This gives an average burst velocity of approximately 170 feet per second.”

NIST’s explanation for these high-velocity bursts of debris is provided not in its final report, but in its FAQs, where it calls them “puffs of smoke” and says, “[T]he falling mass of the building compressed the air ahead of it — much like the action of a piston — forcing smoke and debris out the windows as the stories below failed sequentially.”7

Kevin Ryan offers several arguments for why NIST’s explanation is not valid:

  • The floors were not the kind of tightly sealed, highly pressurized containers that would be required to generate overpressures strong enough to burst windows.
  • The falling mass would need to act as a flat plate exerting uniform pressure at all points. But the falling upper sections, themselves disintegrating as observed in the videos, could not exert uniform pressure.
  • Even if perfect containers and uniform pressure are assumed, using the Ideal Gas Law to calculate the change in pressure, we can determine that the air pressure would not increase enough to burst windows.
  • The bursts contained pulverized debris, not smoke and dust. Yet building materials 20 to 30 stories below the collapse zone could not be pulverized and ejected laterally by air pressure.

Endnotes

[1] Architects & Engineers for 9/11 Truth: Beyond Misinformation: What Science Says About the Destruction of World Trade Center Buildings 1, 2, and 7. Chapter 3, Endnote 13.

[2] NIST: Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Towers (December 1, 2005), p.146.

[3] Ibid.

[4] Bažant, Zdeněk and Le, Jia-Liang: “Why the Observed Motion History of the World Trade Center Towers is Smooth,” Journal of Engineering Mechanics (January 2011).

[5] Jones, Steven: “Why Indeed Did the WTC Buildings Collapse Completely?Journal of 9/11 Studies (September 2006)

[6] Ryan, Kevin: “High Velocity Bursts of Debris from Point-Like Sources in the WTC Towers,” Journal of 9/11 Studies (June 2007).

[7] NIST: Questions and Answers about the NIST WTC Towers Investigation, Question #9.

In addition to the wealth of video and photographic evidence regarding the destruction of the Twin Towers, there is a wealth of eyewitness accounts. The largest source of eyewitness accounts is the New York Fire Department’s (FDNY’s) World Trade Center Task Force Interviews (sometimes referred to as the “FDNY Oral Histories”), which comprise approximately 10,000 to 12,000 pages of statements by over 500 FDNY personnel collected from early October 2001 to late January 2002.1

In its final report on the destruction of the Twin Towers, the National Institute of Standards and Technology (NIST) declared that it found “no corroborating evidence for alternative hypotheses suggesting that the WTC towers were brought down by controlled demolition using explosives planted prior to September 11, 2001.”2 Although it does not elaborate beyond that in its final report, one of the reasons NIST gives in its FAQs is as follows:

“[T]here was no evidence (collected by NIST or by...the Fire Department of New York) of any blast or explosions in the region below the impact and fire floors as the top building sections began their downward movement upon collapse initiation.” 3

This statement ignores and directly contradicts the plethora of accounts from eyewitnesses who reported witnessing explosions, which they consciously identified as such.

The most comprehensive analysis of these accounts, performed by Dr. Graeme MacQueen, a retired professor of Religious Studies at McMaster University, and documented in Chapter 8 of The 9/11 Toronto Report, identifies 156 such eyewitnesses. The vast majority of them — 135, or 87 percent of the total — are first responders, including 121 from the FDNY and fourteen from the Port Authority Police Department. Thirteen are reporters, and the remaining eight MacQueen categorizes as “other,” usually people who worked near WTC 1 and WTC 2.4

MacQueen suggests that the main objection to interpreting these accounts as evidence of controlled demolition is that the observed explosions were some other natural form of explosion that occurs in large fires. However, MacQueen identifies three common characteristics among the accounts that distinguish the explosions in WTC 1 and WTC 2 from the four kinds of explosions that typically occur in fires (boiling-liquid-expanding-vapor-explosions or “BLEVEs”; electrical explosions; smoke explosions or “backdrafts”; and combustion explosions):

Identification: If the explosions encountered were the type typically encountered in fires, the firefighters would be expected to recognize them as such and name them. There are very few instances where they do so. On the contrary, they clearly feel these were different types of explosions than those they were used to encountering...

Power: Many eyewitnesses clearly thought they were watching explosions destroy the Twin Towers. But none of the common four types of fire-related explosions could accomplish this...

Pattern: ...[M]any eyewitnesses reported regular, rapid energetic events in sequence down the building, which cannot be explained by any of the four common types of explosion.

A selection of the eyewitness accounts illustrating the characteristics outlined above (Identification, Power, and Pattern) is presented in Appendix A of Beyond Misinformation: What Science Says About the Destruction of World Trade Center Buildings 1, 2, and 7.

The perception that explosions had destroyed WTC 1 and WTC 2 was so prevalent among firefighters that it became widely discussed. “At that point, a debate began to rage because the perception was that the building looked like it had been taken out with charges,” said Christopher Fenyo in his WTC Task Force Interview. John Coyle recalled in his interview, “I thought it was exploding, actually. That’s what I thought for hours afterwards.... Everybody I think at that point still thought these things were blown up.”

In 2007, a group of scientists, an architect, and two 9/11 family members filed a “Request for Correction” to the NIST report under the Information Quality Act.5 They argued that NIST had, among other problems, ignored the eyewitness evidence of explosions contained in the World Trade Center Task Force Interviews. NIST responded by saying that it had reviewed them, and, “Taken as a whole, the interviews did not support the contention that explosives played a role in the collapse of the WTC Towers” — a markedly different position from the one given in its FAQs, which said that “There was no evidence (collected by...the Fire Department of New York) of any blast or explosions....”

In any case, MacQueen rejects NIST’s assessment, writing in the paper “118 Witnesses: The Firefighters’ Testimony to Explosions in the Twin Towers”:

“We have 118 witnesses out of a pool of 503. Over 23 percent of our group are explosion witnesses. In my judgment, this is a very high percentage of witnesses, especially when we consider...[that Interviewees] were typically not asked about explosions, and, in most cases, were not even asked about the collapses of the towers. What testimony we have was volunteered, and it therefore represents not the maximum number of witnesses to explosions but the minimum number.”6


Endnotes

[1] Fire Department of New York (FDNY): “World Trade Center Task Force Interviews,” The New York Times (October 2001 – January 2002).

[2] NIST: Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Towers (December 1, 2005), p. 146.

[3] NIST: Questions and Answers about the NIST WTC Towers Investigation, Question #8.

[4] A full compilation of the 156 eyewitness accounts identified by Dr. Graeme MacQueen can be viewed at http://AE911Truth.org/downloads/156eyewitnessaccounts.pdf.

[5] McIlvaine, Bob et al. “9/11 Family Members and Scholars: Request for Correction Submitted to NIST,” Journal of 9/11 Studies (2007).

[6] MacQueen, Graeme: “118 Witnesses: The Firefighters’ Testimony to Explosions in the Twin Towers,” Journal of 9/11 Studies (2006). 

Despite the illegal destruction of most of the structural steel and other debris in the months after 9/11, a sizeable body of forensic evidence has been developed over the years by government investigators and independent researchers. Much of the available evidence indicates the occurrence of high-temperature thermitic reactions before, during, and after the destruction of the towers.

NFPA 921: Guide for Fire and Explosion Investigations, which serves as the national guide for fire and explosion investigations in the United States, advises that “All available fuel sources should be considered and eliminated until one fuel can be identified as meeting all the physical damage criteria as well as any other significant data.” [Emphasis added.] On the potential use of exotic accelerants, including thermite, NFPA 921 further advises: “Indicators of exotic accelerants include...melted steel or concrete.”

The National Institute of Standards and Technology (NIST), however, did not follow NFPA 921 in its investigation of the World Trade Center destruction. Instead, it handled the evidence of high-temperature thermitic reactions in much the same way it handled the evidence regarding the structural behavior of the buildings: either denying it, ignoring it, or providing speculative explanations not based upon scientific analysis.

Molten Metal Pouring out of WTC 2

Just before 9:52 AM, molten metal began pouring out of WTC 2 near the northeast corner of the 80th floor and continued to flow with increasing intensity until the collapse at 9:59 AM. NIST provided ample documentation of the pouring molten metal, which it described and hypothesized as follows:

Molten metal pouring out of WTC 2.

“Just over a second [after 9:51:51 AM], a bright spot appeared at the top of one window...and a glowing liquid began to pour from this location.... The composition of the flowing material can only be the subject of speculation, but its behavior suggests it could have been molten aluminum.... The Aluminum Association Handbook...lists the melting point ranges for the alloys [comprising the Boeing 767 structure] as roughly 500°C to 638°C and 475°C to 635°C.... These temperatures are well below those characteristic of fully developed fires (c. 1,000°C)....” 1

But, as Dr. Steven Jones writes in “Why Indeed Did the WTC Buildings Completely Collapse?” this claim is untenable due to the color of the molten metal:

“Is the falling molten metal from WTC Tower 2...more likely molten iron from a thermite reaction OR pouring molten aluminum?

“The yellow color implies a molten metal temperature of approximately 1,000°C, evidently above that which the dark-smoke hydrocarbon fires in the Towers could produce.... Also, the fact that the liquid metal retains an orange hue as it nears the ground...further rules out aluminum....

“We also noted [in our experiments] that...the falling aluminum displayed a silvery-gray color, adding significantly to the evidence that the yellow-white molten metal flowing out from the South Tower shortly before its collapse was NOT molten aluminum.” 2

A thermite reaction.

In its FAQs posted in August 2006, almost a year after the release of its final report, NIST attempted to address the criticism that molten aluminum would have a silvery appearance:

“Pure liquid aluminum would be expected to appear silvery. However, the molten metal was very likely mixed with large amounts of hot, partially burned, solid organic materials... which can display an orange glow, much like logs burning in a fireplace.” 3

Molten aluminum.

While NIST did not test its hypothesis — merely asserting that it was “very likely” — Dr. Jones did:

“NIST states the hypothesis that flowing aluminum with partially burned organic materials mixed in, “can display an orange glow.” But will it really do this? I decided to do an experiment to find out.... Of course, we saw a few burning embers, but this did not alter the silvery appearance of the flowing, falling aluminum....

“In the videos of the molten metal falling from WTC 2 just prior to its collapse, the falling liquid appears consistently orange, not just orange in spots and certainly not silvery. We conclude from all of these studies that the falling metal which poured out of WTC 2 is NOT aluminum.” 4

More than a decade later, NIST still has not conducted its own experiments to verify its hypothesis, nor has it revised its FAQs to account for the results of Dr. Jones’ experiments.

Molten Metal in the Debris

Not only was molten metal seen pouring out of WTC 2, dozens of eyewitnesses observed it in the debris of all three buildings. A small selection is presented below (a comprehensive list of all eyewitness accounts to molten metal can be found in the article “Witnesses of Molten Metal at Ground Zero”):

  • Leslie Robertson, a lead engineer in the design of WTC 1 and WTC 2, told an audience: “We were down at the B-1 level and one of the firefighters said, ‘I think you’d be interested in this.’ And they pulled up a big block of concrete, and there was like a little river of steel flowing.” 5
  • FDNY Captain Philip Ruvolo recalled with other firefighters seated next to him: “You’d get down below and you’d see molten steel, molten steel, running down the channel rails, like you’re in a foundry, like lava.” Other firefighters chimed in: “Like lava.” “Like lava from a volcano.” 6
  • Ken Holden, the Commissioner of the NYC Department of Design and Construction, testified before the 9/11 Commission: “Underground it was still so hot that molten metal dripped down the sides of the wall from Building 6.” 7

This photograph, taken by Frank Silecchia on September 27, 2001, shows a piece of metal being dug up that is salmon-to-yellow color, indicating temperatures from 845°C (1,550°F) to 1,040°C (1,900°F).

According to NIST, the highest temperature reached by the fires was 1,100°C. Yet structural steel does not begin to melt until about 1,482°C (2,700°F). How then did NIST explain the evidence of molten metal?

NIST’s first approach was to omit the evidence of molten metal from its final report. Then, in its August 2006 FAQs, it addressed that evidence with the following question and answer.

13. Why did the NIST investigation not consider reports of molten steel in the wreckage from the WTC towers?

NIST investigators...found no evidence that would support the melting of steel in a jet-fuel ignited fire in the towers prior to collapse. The condition of the steel in the wreckage of the WTC towers (i.e., whether it was in a molten state or not) was irrelevant to the investigation of the collapse since it does not provide any conclusive information on the condition of the steel when the WTC towers were standing....

Under certain circumstances it is conceivable for some of the steel in the wreckage to have melted after the buildings collapsed. Any molten steel in the wreckage was more likely due to the high temperature resulting from long exposure to combustion within the pile than to short exposure to fires or explosions while the buildings were standing.

Each claim in NIST’s answer is demonstrably unscientific:

  • In the first sentence, NIST assumes that the only possible cause of “melting steel” would have been “the jet-fuel ignited fire in the towers,” which is an implausible hypothesis on its face.
  • NIST’s next claim — “The condition of the steel in the wreckage...was irrelevant to the investigation...since it does not provide any conclusive information on the condition of the steel when the WTC towers were standing” — flies in the face of forensic investigation principles. Recall NFPA 921, which explicitly advises, “Indicators of exotic accelerants include...melted steel or concrete.” Furthermore, in science, evidence is not ignored on the basis that it is not conclusive by itself. NIST’s claim is yet more perplexing because molten metal was observed pouring out of WTC 2 — “when the WTC towers were standing” — as NIST documented extensively.
  • NIST’s next claim is simply false. It is impossible for a diffuse hydrocarbon fire to reach temperatures close to the 1,482°C (2,700°F) required to melt steel, particularly in an oxygen-starved debris pile.
  • Finally, with the expression “Any molten steel in the wreckage,” NIST neither confirmed nor denied the existence of molten metal. In an investigation that followed NFPA 921, NIST would have sought to establish whether molten metal was present and, if so, what its source was.

However, outright denial would be the approach used by NIST investigator John Gross. In a talk at the University of Texas in October 2006, he responded to a question about the presence of molten metal with the following answer:

“First of all, let’s go back to your basic premise that there was a pool of molten steel. I know of absolutely nobody, no eyewitness who has said so, nobody who’s produced it. I was on the site. I was on the steel yards. So I don’t know that that’s so. Steel melts at around 2,600°F. I think it’s probably pretty difficult to get that kind of temperatures in a fire.” 8

Iron Spherules and Other Particles in the WTC Dust

Three scientific studies have documented evidence in the WTC dust that indicates extremely high temperatures during the destruction of WTC 1 and WTC 2 — and possibly WTC 7.

The RJ Lee Report

Released in May 2004, the RJ Lee report titled WTC Dust Signature identified “[s]pherical iron and spherical or vesicular silicate particles that result from exposure to high temperature” in the dust.

An earlier 2003 version of RJ Lee’s report observed:

“Various metals (most notably iron and lead) were melted during the WTC event, producing spherical metallic particles. Exposure of phases to high heat results in the formation of spherical particles due to surface tension.... Particles of materials that had been modified by exposure to high temperature, such as spherical particles of iron and silicates, are common in the WTC dust...but are not common in normal office dust.”

The 2003 version also reported that while iron particles make up only 0.04 percent of normal building dust, they constituted 5.87 percent of the WTC dust.

Iron does not melt until 1,538°C (2,800°F), which, as discussed above, cannot be reached by diffuse hydrocarbon fires. Still, even higher temperatures than 1,538°C were indicated by another discovery documented in RJ Lee’s report:

“The presence of lead oxide on the surface of mineral wool indicates the existence of extremely high temperatures during the collapse which caused metallic lead to volatilize, oxidize, and finally condense on the surface of the mineral wool.”

The 2003 version also referred to temperatures “at which lead would have undergone vaporization.” For such vaporization to occur, lead would need to have been heated to its boiling point of 1,749°C (3,180°F).

The USGS Report

Released in 2005, a report by the U.S. Geological Survey (USGS) titled Particle Atlas of World Trade Center Dust identified “trace to minor amounts” of “metal or metal oxides” in the WTC dust and presented micrographs of these particles, two of which were labeled “Iron-rich sphere.”

A scanning electron microscopy image with EDS of an “iron-rich sphere” provided by USGS.

Steven Jones et al.

Published by Dr. Steven Jones and seven other scientists in early 2008, the paper “Extremely high temperatures during the World Trade Center destruction” connected the dots between the earlier RJ Lee and USGS reports. It also provided new observations based on analysis of WTC dust samples obtained by Dr. Jones. According to the authors:

“The formation of spherules in the dust implies the generation of materials somehow sprayed into the air so that surface tension draws the molten droplets into near-spherical shapes. The shape is retained as the droplet solidifies in the air.”

In addition to observing spherules of iron and silicates, their study discussed the presence of molybdenum spherules documented by the USGS study but not included in its report. (This additional data from the USGS study was obtained through a FOIA request.) Molybdenum is known for its extremely high melting point of 2,623°C (4,754°F).

Jones’ study also discussed evidence of even higher temperatures contained in the RJ Lee report (quoting from the RJ Lee report):

A scanning electron microscopy image with EDS of vesicular alumino-silicate provided by RJ Lee.

“Some particles show evidence of being exposed to a conflagration such as spherical metals and silicates, and vesicular particles (round open porous structure having a Swiss cheese appearance as a result of boiling and evaporation).... These transformed materials include: spherical iron particles, spherical and vesicular silicates, and vesicular carbonaceous particles.”

Dr. Jones and his coauthors observed:

“[I]f the “Swiss-cheese appearance” is indeed the result of “boiling and evaporation” of the material as the [RJ Lee] report suggests, we note the boiling temperature for aluminosilicate is approximately 2,760°C.”

They then provided a table summarizing the temperatures needed to account for the various evidence of high temperatures in the World Trade Center destruction, which they contrasted with the much lower maximum temperatures associated with the fires on September 11.

From the paper “Extremely high temperatures during the WTC destruction.”

The closest NIST has come to acknowledging the evidence of extremely high temperatures in the WTC dust was in an email communication with an independent researcher following the release of NIST’s draft report on WTC 7. NIST replied to the researcher’s inquiry with a single sentence: “The NIST investigative team has not seen a coherent and credible hypothesis for how iron-rich spheres could be related to the collapse of WTC 7.”10

Nano-thermite in the WTC Dust

Photomicrographs of red-gray chips from each of the four WTC dust samples. The inset in (d) shows the gray layer of the chips.

In April 2009 a group of scientists led by Dr. Niels Harrit, an expert in nano-chemistry who taught chemistry at the University of Copenhagen for over 40 years, published a paper in the Open Chemical Physics Journal titled “Active Thermitic Materials Discovered in Dust from the 9/11 World Trade Center Catastrophe.” 11 This paper, which reported the results of experiments conducted on small red-gray, bi-layered chips found in multiple independent WTC dust samples, concluded that the chips were unreacted nano-thermite, a form of thermite with explosive properties engineered at the nano-level.

According to their analyses, the gray sides of the chips consisted of “high iron and oxygen content including a smaller amount of carbon,” while the red sides had various features indicative of thermite and nano-thermite.

Features Indicative of Thermite

  • The chips were composed primarily of “aluminum, iron, oxygen, silicon, and carbon.” The first three elements are suggestive of thermite, which is commonly made by combining aluminum and iron oxide.
  • Their red color and magnetic properties were suggestive of iron.
  • They all ignited between 415° and 435°C, producing highly energetic reactions.

Features Indicative of Nano-thermite

  • The chips’ primary ingredients were ultra-fine grain, seen typically “in particles at the scale of tens to hundreds of nanometers.”
  • The ultra-fine ingredients were intimately mixed.
  • When a flame was applied to them, it resulted in a “high-speed ejection of a hot particle.”
  • They ignited at a much lower temperature — 430°C — than the temperature at which conventional thermite ignites, which is above 900°C.
  • Silicon was one of their main ingredients, and it was porous, suggesting the thermitic material was mixed in a sol-gel to form a porous reactive material.
  • Their carbon content was significant. The authors noted that this “would be expected for super-thermite formulations in order to produce high gas pressures upon ignition and thus make them explosive.”

A backscattered electron image of a red-gray chip.

The presence of the above-described substance in the WTC dust strongly suggests that nano-thermite was used in the destruction of WTC 1, WTC 2, and WTC 7.

What other explanations for this substance exist?

The first possibility is that the red-gray chips were in fact paint chips. The researchers explored this possibility — first by soaking the chips in methyl ethyl ketone (a solvent known to dissolve paint chips, which did not succeed in dissolving the red- gray chips), and second by exposing the red-gray chips and known paint chips to a hot flame. The paint chips dissolved into ash, while the red-gray chips did not.

The second possibility is that the WTC dust might somehow have been contaminated with the red-gray chips during the cleanup operation. However, this hypothesis was ruled out on the basis that all four of the dust samples had been collected at times or places that precluded any contamination. One sample was collected about 20 minutes after the collapse of WTC 1. Of the other three samples, two were collected the next day.

With those two possibilities ruled out, no other plausible explanation has been provided — nor has NIST responded to the reported discovery of nano-thermite in the WTC dust.

Therefore, the presence of unreacted nano-thermite in the WTC dust — which is corroborated by other evidence of high-temperature chemical reactions — constitutes compelling evidence that WTC 1, WTC 2, and WTC 7 were destroyed by controlled demolition using nano-thermite and possibly other explosive and incendiary materials.

NIST’s Refusal to Test for Explosives or Thermite Residues

Despite the compelling evidence for high-temperature thermitic reactions examined above, NIST has refused to test for explosives or thermite residues. NIST provides the following question and answer in its FAQs on WTC 1 and WTC 2:

Was the steel tested for explosives or thermite residues?

NIST did not test for residues of these compounds in the steel.... Analysis of the WTC steel for the elements in thermite/thermate would not necessarily have been conclusive. The metal compounds also would have been present in the construction materials making up the WTC towers, and sulfur is present in the gypsum wall- board that was prevalent in the interior partitions.

But, to reiterate the point mentioned above, evidence is not ignored in science just because it is not conclusive. In fact, NIST conducted many tests during the course of its investigation that were not conclusive. Given the evidence examined in this chapter, some of which had already been discussed widely during NIST’s investigation, NIST had every reason to conduct very simple lab tests for explosives and thermite residues, regardless of whether or not such testing would have been conclusive.

Moreover, NIST’s answer actually implies that such testing might have been conclusive. Indeed, a negative result would certainly be conclusive. A positive result could also have been conclusive. This argument was made in the Appeal of NIST’s response to a Request for Correction filed in 2007 by a group of scientists, an architect, and two 9/11 family members, which quoted the following statement from Materials Engineering, Inc.:

“When thermite reaction compounds are used to ignite a fire, they produce a characteristic burn pattern, and leave behind evidence. The compounds are rather unique in their chemical composition.... While some of these elements are consumed in the fire, many are also left behind in the residue.... The results [of Energy Dispersive Spectroscopy on minute traces of residue], coupled with visual evidence at the scene, provide absolute certainty that thermite reaction compounds were present....”

The Appeal therefore argued:

“[I]t is difficult to imagine a scenario in which a test for explosive residues would not be conclusive.... Unless NIST can explain a plausible scenario that would produce inconclusive explosive residue test results, its stated reason for not conducting such tests is wholly unpersuasive.”

NIST ignored this point in its response to the Appeal and provided no such scenario.

Summary

In summary, NIST provided woefully inadequate and erroneous explanations for the molten metal seen pouring out of WTC 2 and in the debris of all three buildings. Furthermore, NIST provided no explanation for evidence of extremely high temperatures in the WTC dust, except to deny that a coherent and credible hypothesis to explain it existed. Finally, NIST has not commented on the discovery of unreacted nano-thermite in the WTC dust.


Endnotes

[1] NIST: NCSTAR 1-5A, pp. 374–376.

[2] Jones, Steven: “Why Indeed Did the WTC Buildings Collapse Completely?Journal of 9/11 Studies (September 2006).

[3] NIST: Questions and Answers about the NIST WTC Towers Investigation, Question #21.

[4] Jones, Steven: “Why Indeed Did the WTC Buildings Collapse Completely?Journal of 9/11 Studies (September 2006).

[5] https://youtu.be/lDnbfXLUyI4

[6] https://youtu.be/nsw2j-3MCMg

[7] https://youtu.be/KtyrMt7GzyE

[8] https://youtu.be/wcqf5tL887o

[9] Jones, Steven (et al.): “Extremely High Temperatures during the World Trade Center Destruction,” Journal of 9/11 Studies (February 2008).

[10] Griffin, David Ray: The Mysterious Collapse of World Trade Center 7 (2009), pp. 43, 282. Griffin describes an email exchange between researcher Shane Geiger and NIST public affairs officer Gail Porter, which Geiger shared with Griffin.

[11] Harrit, Niels (et al.): “Active Thermitic Materials Discovered in Dust from the 9/11 World Trade Center Catastrophe,” Open Chemical Physics Journal (April 2009).

[12] McIlvaine, Bob et al.: "Appeal Filed with NIST, Pursuant to Earlier Request for Correction," Journal of 9/11 Studies (October 2007). 

The seven-year quest to produce an official technical explanation for the destruction of World Trade Center Buildings 1, 2, and 7 represents an unparalleled case study in “expectation bias."

NFPA 921: Guide for Fire and Explosion Investigations, which serves as the national guide for fire and explosion investigations in the United States, defines “expectation bias” as follows:

“Expectation bias is a well-established phenomenon that occurs in scientific analysis when investigator(s) reach a premature conclusion without having examined or considered all of the relevant data. Instead of collecting and examining all of the data in a logical and unbiased manner to reach a scientifically reliable conclusion, the investigator(s) uses the premature determination to dictate investigative processes, analyses, and, ultimately, conclusions, in a way that is not scientifically valid. The introduction of expectation bias into the investigation results in the use of only that data that supports this previously formed conclusion and often results in the misinterpretation and/or the discarding of data that does not support the original opinion. Investigators are strongly cautioned to avoid expectation bias through proper use of the scientific method.”

NFPA 921 also explicitly urges investigators to avoid presumption in the formulation of hypotheses:

“Until data have been collected, no specific hypothesis can be reasonably formed or tested. All investigations of fire and explosion incidents should be approached by the investigator without presumption…until the use of scientific method has yielded testable hypotheses, which cannot be disproved by rigorous testing.”

As discussed below, the two official investigations of the WTC destruction flagrantly violated these principles, resulting in incomplete hypotheses that are wholly unsupported by any evidence and that ignore most of the relevant evidence.

The WTC FEMA Building Performance Study

“‘It appeared to me that charges had been placed in the building,’ said Mr. Hamburger, chief structural engineer for ABS Consulting in Oakland, Calif. Upon learning that no bombs had been detonated, ‘I was very surprised.’”

This quote from Ronald Hamburger appeared in The Wall Street Journal on September 19, 2001. By that time, Hamburger was one of a team of engineers that had been assembled by the American Society of Civil Engineers (ASCE) and that would be given authority under FEMA to investigate the World Trade Center destruction. He would also be named “Chapter Leader” for the chapter on WTC 1 and WTC 2 in FEMA’s final report.

How did Ronald Hamburger learn that “no bombs had been detonated?” FEMA’s investigators were not granted access to the site until the week of October 7. Thus, neither he nor anyone else had conducted forensic analysis of the debris, nor had they interviewed eyewitnesses. From a scientific perspective, as codified NFPA 921, there was no basis for disconfirming his initial hypothesis.

The likely answer is that between September 11 and the time that he was interviewed, the government and the media had put forth an account of the day’s events that was incompatible with his original assessment that the buildings had been brought down with explosives. Therefore, as Hamburger essentially stated, he ruled out his initial hypothesis when he “learned” that the official account did not include explosives being used to bring down the buildings.

Even though the destruction of WTC 1 and WTC 2 appeared to many to be caused by explosives, and despite the fact that no steel-framed high-rise had ever collapsed due to fire, the FEMA investigation proceeded with fire-induced failure as its only hypothesis. In addition, the investigative team was subject to significant external constraints. As New York Times reporters James Glanz and Eric Lipton wrote:

"[T]he investigation was financed and given its authority by [FEMA], with which [lead investigator Gene] Corley’s team had a shaky relationship from the start. For months after September 11, the investigators...were unable to persuade FEMA to obtain basic data like detailed blueprints of the buildings that collapsed. Bureaucratic restrictions often kept the engineers from interviewing witnesses to the disaster, making forensic inspections at ground zero, or getting crucial information like recorded distress calls from people trapped in the buildings. For reasons that would remain known only to FEMA, the agency refused to let the team appeal to the public for photographs and videos of the towers that could help with the investigation.” 1

Most detrimental to the team’s ability to conduct forensic analysis was the City’s recycling of the buildings’ steel, which continued despite requests from the investigators — and outcry among the victims’ families and the fire safety community — for the steel to be saved.2 Although investigators were eventually granted access to the scrap yards, nearly all of the steel, including most of the steel from the upper floors of WTC 1 and WTC 2, was destroyed before it could be inspected.3

FEMA released its report, titled World Trade Center Building Performance Study: Data Collection, Preliminary Observations, and Recommendations, on May 1, 2002. As implied in the title, the report did not attempt to provide a definitive explanation for the destruction of each building. Instead, it posited scenarios in general terms and recommended further investigation to definitively determine the exact causes.

 FEMA’s scenario for WTC 1 and WTC 2 — which reflected common thinking at that time but was later ruled out by the National Institute of Standards and Technology (NIST) — is what became known as the “pancake theory.” According to this hypothesis, the fires caused the floor trusses to lose their rigidity and sag. As a result of the sagging, the column-to-truss connections failed and the floors collapsed onto the floors below them. This precipitated “an immediate progressive series of floor failures,” which left behind “tall freestanding portions of the exterior wall and possibly central core columns.” FEMA then stated, “As the unsupported height of these freestanding exterior wall elements increased, they buckled at the bolted column splice connections, and also collapsed. Perimeter walls of the building seem to have peeled off and fallen directly away from the building face, while portions of the core fell in a somewhat random manner.”

Figure 2-21 from the FEMA report depicts a failed floor truss falling on the floor below it and the buckling of columns that were previously receiving lateral support from that floor truss.

The NIST Investigation

Amid a growing sense that the FEMA investigation was insufficient for the task of conducting a full-scale investigation, NIST began planning its own investigation in October 2001 to eventually succeed FEMA’s. The NIST investigation was announced on August 21, 2002, and was scheduled to take 24 months.

In its final plan, released in August 2002, NIST acknowledged that fire had never caused the total collapse of a high-rise building prior to September 11, 2001. Nonetheless, it pursued this hypothesis without reservation, even going so far as to treat it as fact: “The WTC Towers and WTC 7 are the only known cases of total structural collapse in high-rise buildings where fire played a role.”

In its second progress report, released in May 2003, NIST laid out three leading hypotheses for the destruction of WTC 1 and WTC 2. One was FEMA’s “pancake theory” involving the failure of floor connections. Another hypothesis suggested that the floor connections held strong, which then caused the sagging floors to pull the exterior columns inward until they buckled. This would become the main initiating mechanism in NIST’s “Probable Collapse Sequence.” The third hypothesis posited direct fire-induced column failure.

In June 2004, NIST released a third, much more extensive progress report containing interim findings and a working hypothesis for the destruction of WTC 1 and WTC 2. Although the working hypothesis described the overall sequence of events from airplane impact to collapse initiation in relatively clear steps, NIST did not settle on any of the three hypotheses outlined in the previous progress report or on a location in either building where the initiating failure might have occurred.

In September 2005, NIST released its final report on WTC 1 and WTC 2. The table below is a summary of NIST’s “Probable Collapse Sequence.”

A summary of NIST’s “Probable Collapse Sequence.”

As mentioned above, the main initiating mechanism in NIST’s “Probable Collapse Sequence” involves the sagging of thermally weakened floor trusses pulling exterior columns inward until some of the exterior columns buckled, which then caused instability to spread to the other columns. The tops of the buildings above where the failures occurred then tilted in the direction of the failed walls and began to fall. According to NIST, at this point, global collapse became inevitable as the stories below the level of collapse provided little resistance.

This PBS NOVA animation shows the mechanism that NIST claims initiated the collapse of WTC 1 and WTC 2: thermally weakened floor trusses pulling exterior columns inward to the point of buckling.

As researcher Frank Legge points out, “the fire based official explanation is a series of events, like links in a chain, while the explosive based explanation is a parallel set of scientific studies of evidence…. If an explanation is in the form of a chain it is only necessary to prove one link wrong to destroy the case.” 4

Below we focus on NIST’s failed attempts to prove three links in that chain: Fireproofing Dislodgment, Heating of Structural Members, and Collapse Initiation and Progression.

For discussion of NIST’s failure to analyze and explain why total collapse ensued after collapse initiation, see Near-Free-Fall Acceleration and Explosive Features. For more extensive critiques of NIST’s explanation for the destruction of WTC 1 and WTC 2, see the items above under “More on this Subject.”

Fireproofing Dislodgement

The fire protection in WTC 1 and WTC 2 consisted primarily of “sprayed fire-resistive material,” or SFRM. Some columns also had gypsum wallboard enclosures, and some had a combination of both.

A photograph of WTC trusses with fireproofing.

NIST’s “Probable Collapse Sequence” depends heavily upon the dislodgement of these materials by the airplane impacts. In its final report, NIST concluded:

“The WTC towers likely would not have collapsed under the combined effects of aircraft impact damage and the extensive, multi-floor fires that were encountered on September 11, 2001, if the thermal insulation had not been widely dislodged or had been only minimally dislodged by the aircraft impact.” 5

Yet NIST produced remarkably little evidence to support its claim that fireproofing dislodgement significantly affected the structures.

Because such dislodgement would not have been visible from outside the buildings, the extent of dislodgement had to be estimated based on where NIST’s aircraft impact simulations predicted damage to wall partitions or furnishings. At the very end of its investigation, NIST finally performed physical testing “to provide evidence regarding the assumption that...the SFRM used for thermal insulation of structural members was damaged and dislodged.” This testing, contained in NIST’s “Debris Impact Study,” involved shooting 15 rounds from a shotgun at a flat steel plate and a metal bar coated with fireproofing inside a plywood box. Referring to that experiment, Kevin Ryan writes:

A photograph from NIST’s “Debris Impact Study.”

“[I]t’s not hard to see that these tests actually disproved their findings.... Nearly 100,000 blasts would have been needed based on NIST’s own damage estimates, and these would have to be directed in a very symmetrical fashion to strip the columns and floors from all sides....

“To put NIST’s pivotal claim to rest, there was simply no energy available to cause fireproofing loss. Previous calculations by engineers at MIT had shown that all the kinetic energy from the aircraft was consumed in breaking columns, crushing the floors and destroying the aircraft itself. But NIST’s tests indicate that 1 MJ of energy was needed per square meter of surface area to sheer the fireproofing off.... [T]he extra energy needed would be several times more than the amount of kinetic energy available to begin with.” 6

Moreover, fireproofing dislodgement could not have contributed to the collapse of WTC 1, because it did not occur where the collapse initiated. The collapse of WTC 1 started at the 98th floor. Yet, according to NIST, no fireproofing was dislodged on any of the core columns on the 98th floor or on the floor trusses supporting the 99th floor.

Heating of Structural Members

Although nearly all of the WTC steel was destroyed before it could be inspected, NIST was able to obtain “about 236 pieces of WTC steel,” as reported in its December 2003 Public Update. NIST explained that “[r]egions of impact and fire damage were emphasized in the selection of the steel for the Investigation.” It then declared, “NIST believes that this collection of steel from the WTC Towers is adequate for the purposes of the Investigation.”

This photograph shows the mud cracking of paint on the WTC steel after exposure to 250°C for one hour. Only three out of 170 tested areas on recovered exterior columns reached 250°C.

Out of the more than 170 areas that NIST tested on recovered exterior columns, it found only three locations that bore evidence of the steel reaching temperatures above 250°C. NIST also found that the steel “show[ed] no evidence of exposure to temperatures above 600°C for any significant time.” It obtained similar results from the two core columns recovered from the fire-affected floors.7 NIST therefore conceded:

“From the limited number of recovered structural steel elements, no conclusive evidence was found to indicate that pre-collapse fires were severe enough to have a significant effect on the microstructure that would have resulted in weakening of the steel structure.” 8

However, despite its initial declaration that the collected steel was “adequate for the purposes of the investigation,” NIST’s report downplays the results of its testing, frequently reminding the reader that the exterior columns it tested were only three percent of the exterior columns on the fire floors and thus “cannot be considered representative of other columns on these floors.”

From a statistical perspective, though, 170 areas is not an insignificant sample size from which to extrapolate, particularly when “regions of impact and fire damage were emphasized” and less than two percent of the sample reached temperatures above 250°C — not to mention the temperatures of 600° and higher used in NIST’s computer model.

In 2007, a group of scientists, an architect, and two 9/11 family members filed a “Request for Correction” to the NIST report under the Information Quality Act.9 They requested that, among other things, NIST’s report “be revised to make its computer simulation conditions actually simulate physical reality.” The Request noted:

“NIST has provided no justification whatsoever for allowing its computer simulations to heat the steel to temperatures well above 600°C when its own physical tests reveal that little, if any, of the steel inside the WTC ever reached 600°C.”

Yet NIST’s response to the Request for Correction completely ignored the 170 areas on the exterior columns that NIST had tested. Instead, the response focused solely on the two core columns that it had also tested, making the obvious claim that they were too small a sample size from which to extrapolate. And it asserted the validity of its fire modeling, which, however informative, tells us nothing conclusive about the temperatures that the steel reached.10

Collapse Initiation and Progression

Because most of the WTC steel was destroyed before it could be inspected, the NIST WTC investigation had to rely almost entirely on computer modeling. The modeling performed by NIST failed — effectively disproving its hypothesis — in two ways:

1. It did not replicate the observed structural behavior of the buildings, and

2. It required significant manipulation — in other words, applying information known to be factually unsupported — in order to achieve collapse initiation.

First, as discussed elsewhere, NIST provided no modeling to support its claim that the upper sections of WTC 1 and WTC 2 could accelerate through 92 stories and 76 stories, respectively, of intact structure “essentially in free fall.” NIST later admitted, “[B]ecause of the magnitude of deflections and the number of failures occurring, the computer models are not able to converge on a solution.... [W]e were unable to provide a full explanation of the total collapse.”11 NIST also refused to provide visualizations of its models showing collapse initiation.12

Among the many ways in which NIST manipulated its modeling of WTC 1 and WTC 2, two are critical to NIST’s “Probable Collapse Sequence.” First, the results of NIST’s physical testing on floor assemblies subjected to fire conditions of 2,000°F showed that the floors sagged four inches after 60 minutes of exposure and six inches after 100 minutes of exposure, which were the approximate durations of the fires in WTC 2 and WTC 1, respectively.13 However, NIST’s modeling allowed for sagging of more than 42 inches.

This illustration from the NIST report shows a floor truss sagging 42 inches.

In its response to the 2007 Request for Correction and in its FAQs, NIST claimed that the floor assembly testing was not intended to be relevant to its structural analysis: Only fireproofed floor assemblies were tested, whereas the fireproofing on September 11 was widely dislodged. But the authors of the Request for Correction rejected that claim for a number of reasons:

1. What was the purpose of the testing if it was not to analyze the thermal-structural response of the towers?

2. The tested floor assemblies actually had less fireproofing on them than the real WTC floor assemblies.

3. NIST did not substantiate its claim that fireproofing dislodgement significantly affected the structures, as discussed above.

4. The duration of the fires in the testing was much longer than the duration of the fires in the areas where NIST claimed the floors sagged.14

The second critical way in which NIST manipulated its modeling of WTC 1 and WTC 2 was to artificially induce the inward bowing of exterior columns to the point of buckling (which NIST claimed initiated the collapses). Because NIST’s model showed that floor sagging did not cause the exterior columns to bow inward to the point of failing, NIST applied an artificial lateral load of 5,000 pounds to each column from outside the building in order to make the exterior columns fail. In a feat of circular logic, NIST justified doing so in order to match the observed inward bowing.15

Did NIST provide ‘extraordinary evidence’ to support its hypothesis?

In his 2009 book The Mysterious Collapse of World Trade Center 7, preeminent 9/11 researcher David Ray Griffin commented that a key principle of the scientific method is as follows: “Unprecedented causes should not, without good reasons, be posited to explain familiar occurrences. Given the regularity of nature—which is both assumed and continually confirmed by science—we properly assume, unless there is extraordinary evidence to the contrary, that each instance of a familiar occurrence was produced by the same causal factors that brought about previous instances."16

In the case at hand, the familiar occurrence was the total destruction of the three steel-framed high-rises, which, prior to September 11, 2001, had resulted numerous times from the procedure of controlled demolition, and never from fire. In order for fire to be posited as the cause of these three catastrophic collapses, “extraordinary evidence to the contrary” should be called for.

The inability of investigators at FEMA and NIST to construct a plausible explanation involving fire-induced failure, supported by sound scientific analysis, illustrates not just the absence of “extraordinary evidence," but the absence of any evidence at all.


Endnotes

[1] Glanz, James and Lipton, Eric: City in the Sky: The Rise and Fall of the World Trade Center (2003), p. 330.

[2] Ibid., pp. 330–332.

[3] U.S. House of Representatives Committee on Science: Hearing: The Investigation of the World Trade Center Collapse: Findings, Recommendations, and Next Steps (May 1, 2002), p. 27.

[4] Legge, Frank: “9/11 and Probability Theory,” Journal of 9/11 Studies (June 2008).

[5] NIST: Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Towers (December 1, 2005), p. xxxviii.

[6] Ryan, Kevin: “What is 9/11 Truth? – The First Steps,” Journal of 9/11 Studies (August 2006).

[7] NIST: NCSTAR 1-3, p. xli.

[8] NIST: NCSTAR 1-3C, p. 235.

[9] McIlvaine, Bob et al. “9/11 Family Members and Scholars: Request for Correction Submitted to NIST,” Journal of 9/11 Studies (2007).

[10] NIST: Response to the Request for Correction (September 2007).

[11] Ibid.

[12] Parker, David: “WTC investigators resist call for collapse visualization,” New Civil Engineer (October 6, 2005).

[13] NIST: NCSTAR 1-6B, Chapters 4 and 5. Note: NIST’s floor assembly tests were conducted on half-size trusses.

[14] McIlvaine, Bob et al.: Appeal Filed with NIST, Pursuant to Earlier Request for Correction (November 2007).

[15] NIST: NCSTAR 1-6D, pp. 180, 181, and Appendix A.

[16] Griffin, David Ray: The Mysterious Collapse of World Trade Center 7 (2009), p. 23. 

Today, the National Institute of Standards and Technology (NIST) acknowledges that WTC 7 fell at a rate of free fall (or the rate of gravity) for a period of approximately 2.25 seconds before it started to slow down.1 David Chandler, a physics teacher who has studied the behavior of WTC 7 extensively, explains the significance of free fall in the article titled “Free Fall and Building 7 on 9/11”: 2

WTC 7 is shown falling symmetrically into its own footprint. It accelerated at free fall for 2.25 seconds of its descent.

“Newton’s third law says that when objects interact, they always exert equal and opposite forces on each other. Therefore, while an object is falling, if it exerts any force on objects in its path, those objects must push back, slowing the fall. If an object is observed to be in free fall, we can conclude that nothing in the path exerts a force to slow it down....”

Applying this to WTC 7, he explains:

“[F]ree fall is not consistent with any natural scenario involving weakening, buckling, or crushing because in any such a scenario there would be large forces of interaction with the under- lying structure that would have slowed the fall.... Natural collapse resulting in free fall is simply not plausible....”

Chandler and others therefore interpret WTC 7’s free fall as evidence of controlled demolition. How does NIST explain the occurrence of free fall according to its hypothesis of fire-induced failure? To answer that question satisfactorily, we must first examine NIST’s initial attempt to deny the occurrence of free fall.

NIST’s Denial of Free Fall

On August 21, 2008 — six years to the day after NIST’s World Trade Center investigation was first announced — NIST released its draft report on WTC 7 for public comment. In it, NIST described the collapse time of WTC 7 as being 40 percent longer than the time it would take to collapse in free fall:

“The time the roofline took to fall 18 stories was 5.4 s[econds].... Thus, the actual time for the upper 18 floors of the north face to collapse, based on video evidence, was approximately 40 percent longer than the computed free fall time....” 3

NIST repeated this claim in its Questions and Answers about the NIST WTC 7 Investigation (WTC 7 FAQs), stating unequivocally, “WTC 7 did not enter free fall.” NIST’s lead investigator, Dr. Shyam Sunder, repeated it again at NIST’s WTC 7 Technical Briefing on August 26, 2008, when asked the following question, which had been submitted by David Chandler:

Chandler: “Any number of competent measurements using a variety of methods indicate the northwest corner of WTC 7 fell with an acceleration within a few percent of the acceleration of gravity. Yet your report contradicts this, claiming 40 percent slower than free fall, based on a single data point. How can such a publicly visible, easily measurable quantity be set aside?”

Dr. Sunder responded by articulating the meaning of free fall in the clearest terms possible, but denied that is what happened in the case of WTC 7:

Dr. Shyam Sunder explains the meaning of free fall at NIST’s WTC 7 Technical Briefing on August 26, 2008.

Sunder: “[A] free-fall time would be an object that has no structural components below it.... What the analysis shows...is that same time it took for the structural model to come down...is 5.4 seconds. It’s about 1.5 seconds, or roughly 40 percent, more time for that free fall to happen. And that is not at all unusual because there was structural resistance that was provided in this particular case.”

NIST’s Alleged 5.4-Second Collapse Time

The reason for the discrepancy between Chandler’s measurement and NIST’s measurement is contained in Dr. Sunder’s statement above, where he explains that NIST’s computer model showed a collapse time of 5.4 seconds. As Chandler comments in Part 1 of the video series NIST Finally Admits Free Fall:

“Don’t you find it interesting that the 5.4 seconds [NIST] measured for the collapse time just happens to exactly match the theoretical prediction of their model? That kind of precision is incredibly rare when modeling real world events.”

Indeed, when we count backwards 5.4 seconds from the point at which the roofline disappears from view, we find that there is no obvious, continuous movement of the building that could be reasonably interpreted as the start of the collapse. According to Chandler, “Since their model predicted 5.4 seconds for the 18-story collapse, they dutifully conjured up a 5.4-second measurement to match [the model].” Then, NIST assumed that the downward acceleration during those 5.4 seconds was “approximately constant” 4 — even though the building was almost entirely motionless for more than a second. Based upon this inaccurate characterization of WTC 7’s motion, NIST denied the occurrence of free fall.

NIST’s Acknowledgment of Free Fall

To the surprise of many observers, NIST reversed its position in its final report, acknowledging that WTC 7 did enter free fall for 2.25 seconds. But NIST still maintained the total collapse time of 5.4 seconds, which now comprised three separate stages:

  • Stage 1 (0 to 1.75 seconds): acceleration less than that of gravity (i.e., slower than free fall)
  • Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall)
  • Stage 3 (4.0 to 5.4 seconds): decreased acceleration, again less than that of gravity 5

However, in the first stage — which NIST characterizes as “a slow descent with acceleration less than that of gravity that corresponded with the buckling of the exterior columns at the lower floors” — the building is actually nearly motionless. By asserting a first stage in which we are to imagine “the buckling of exterior columns” causing “a slow descent,” NIST is obscuring an important feature of WTC 7’s free fall: its sudden onset. In Part 3 of the video series NIST Finally Admits Free Fall, Chandler observes:

“What is particularly striking is the suddenness of onset of free fall. Acceleration doesn’t build up gradually. The graph [plotting the rate of acceleration] simply turns a corner. The building went from full support to zero support instantly....”

Chandler then describes a second important feature of WTC 7’s free fall:

“The onset of free fall was not only sudden, it extended across the whole width of the building. My measurement of the acceleration was based on the northwest corner. NIST’s recent measurement confirming free fall was based on a point midway along the roofline.”

Taking the rate of acceleration, suddenness, and symmetry of WTC 7’s descent into account, Chandler concludes:

David Chandler’s graph from Part 3 of “NIST Finally Admits Free Fall” plots the velocity of WTC 7’s roofline versus time. The slope shows a free-fall rate of acceleration. The sudden change in slope shows the sudden onset of free fall.

“The collapse we see cannot be due to a column failure, or a few column failures, or a sequence of column failures. All 24 interior columns and 58 perimeter columns had to have been removed over the span of eight floors low in the building simultaneously to within a small fraction of a second, and in such a way that the top half of the building remains intact and uncrumpled.”

While the hypothesis of controlled demolition explains WTC 7’s free fall readily, simply, and completely, NIST’s final report provided no explanation for how free fall was accomplished. It simply asserted, “The three stages of collapse progression described above are consistent with the results of the global collapse analyses discussed in Chapter 12 of NIST NCSTAR 1-9,” (the chapter that presents the results of NIST’s “global model”). But that statement is incorrect. As discussed in The Official Theory, the free fall in Stage 2 is not shown in NIST’s model.


Endnotes

[1] NIST: NCSTAR 1A, p. 48.

[2] Chandler, David: “Free Fall and Building 7 on 9/11,” (Reprinted by AE911Truth in April 2014).

[3] NIST: NCSTAR 1A Draft Report, p. 41.

[4] NIST: NCSTAR 1A Draft Report, p. 40. The term “descent speed,” used in the cited sentence, was an error made by NIST. “Acceleration” was meant.

[5] This condensed description of the three stages of WTC 7’s collapse appears in NIST’s WTC 7 FAQs. 

The National Institute of Standards and Technology (NIST) claims in its WTC 7 FAQs that “no blast sounds were heard on audio tracks of video recordings during the collapse of WTC 7 or reported by witnesses.” 1 However, both audio recordings and eyewitness accounts of explosions during the destruction of WTC 7 contradict NIST’s claim.

Although there are not nearly as many eyewitness accounts of explosions in WTC 7 as in WTC 1 and WTC 2, there are a handful of accounts that strongly suggest explosions occurred immediately before and during WTC 7’s destruction. These include:

  • Craig Bartmer, former NYPD officer: “[A]ll of a sudden...I looked up, and... [t]he thing started peeling in on itself.... I started running...and the whole time you’re hearing “thume, thume, thume, thume, thume.” I think I know an explosion when I hear it.” 2
  • First-year NYU medical student identified as Darryl: “[W]e heard this sound that sounded like a clap of thunder.... [T]urned around — we were shocked.... [I]t looked like there was a shockwave ripping through the building and the windows all busted out.... [A]bout a second later the bottom floor caved out and the building followed after that.” 3
  • Kevin McPadden, unaffiliated, volunteer first responder: “And then it was like another two, three seconds, you heard explosions. Like BA-BOOOOOM! And it’s like a distinct sound...BA-BOOOOOM! And you felt a rumble in the ground, like, almost like you wanted to grab onto something.” 4

MSNBC reporter Ashleigh Banfield hears a loud sound from several blocks north of WTC 7 and says, “Oh my god.... This is it.”

These eyewitness accounts are corroborated by MSNBC video footage of reporter Ashleigh Banfield several blocks north of WTC 7. In the video, she hears a loud sound, turns her attention to WTC 7, and says, “Oh my god.... This is it.” 5 About seven seconds after she hears the loud sound, WTC 7 collapses. As David Chandler observes in the video WTC 7: Sound Evidence for Explosions:

“There were two blasts, followed by seven more regularly spaced all in two and a half seconds. Craig Bartmer’s testimony may come to mind: ‘The whole time you’re hearing “thume, thume, thume, thume, thume.”’....

“When we hear the sharp, regular series of sounds in the background, the building has not yet started to fall. When we hear the reporter say, “This is it,” the building has not yet started to fall.... The blasts we heard occurred seconds before the building started to fall.”

In addition to eyewitness accounts of explosions at the time of WTC 7’s destruction, there were eye-witness accounts from two men — Michael Hess (Corporation Counsel for the City of New York) and Barry Jennings (Deputy Director of Emergency Services at the New York City Housing Authority) — who reported experiencing an explosion and smoke in a stairway in the northeast part of WTC 7 prior to the collapse of WTC 1 at 10:28 AM.6

It has been claimed that what Hess and Jennings experienced was the result of debris from WTC 1 impacting WTC 7. However, this claim is not plausible, as Hess and Jennings were in a stairway at the opposite end of WTC 7 (northeast) from where debris impacted the building (southwest), and their account indicates that the explosion and smoke they witnessed occurred before the collapse of WTC 1.7


Endnotes

[1] NIST: Questions and Answers about the NIST WTC 7 Investigation, Question #13.

[2] https://youtu.be/xpoAmEGdsn4

[3] http://whatreallyhappened.com/IMAGES/wtc7_med2.wma

[4] https://youtu.be/b4z-Wrp1pY8

[5] https://youtu.be/ERhoNYj9_fg?t=2m6s

[6] Hess: https://youtu.be/6e3K9jcPdXc; Jennings: https://youtu.be/gwJi0R2jza4

[7] Griffin, David Ray: The Mysterious Collapse of World Trade Center 7 (2009), pp. 84-111.

In a New York Times article published in February 2002, James Glanz and Eric Lipton wrote:

“Perhaps the deepest mystery uncovered in the investigation involves extremely thin bits of steel collected...from 7 World Trade Center.... The steel apparently melted away, but no fire in any of the buildings was believed to be hot enough to melt steel outright.... A preliminary analysis at Worcester Polytechnic Institute [WPI]...suggests that sulfur released during the fires—no one knows from where—may have combined with atoms in the steel to form compounds that melt at lower temperatures.” 1

The WPI professors, who were “shocked” by the “Swiss cheese appearance” 2 of the steel, reported their analysis in Appendix C of the FEMA WTC Building Performance Study, making the following recommendation:

“The severe corrosion and subsequent erosion of Samples 1 and 2 are a very unusual event. No clear explanation for the source of the sulfur has been identified.... A detailed study into the mechanisms of this phenomenon is needed....” 3

A simple explanation for the source of sulfur, as well as the high-temperature corrosion and erosion, is “thermate,” which is produced when sulfur is added to thermite. In “Revisiting 9/11—Applying the Scientific Method,” Dr. Steven Jones explains:

“When you put sulfur into thermite it makes the steel melt at a much lower temperature, so instead of melting at about 1,538°C it melts at approximately 988°C, and you get sulfidation and oxidation in the attacked steel....

“The thermate reaction proceeds rapidly and is in general faster than basic thermite in cutting through steel due to the presence of sulfur.” 4

How did NIST respond to FEMA’s recommendation?

First, NIST ignored it — thus ignoring what the The New York Times called “perhaps the deepest mystery uncovered in the investigation.”

The eroded, sulfidated steel from WTC 7 at the scrapyard before it was cut off and taken for testing.

Second, NIST claimed that no identifiable steel was recovered from WTC 7, providing the following answer in its WTC 7 FAQs:

“Once [debris] was removed from the scene, the steel from WTC 7 could not be clearly identified. Unlike pieces of steel from WTC 1 and WTC 2, which were painted red and contained distinguishing markings, WTC 7 steel did not contain such identifying characteristics.” 5

Third, when asked at NIST’s WTC 7 Technical Briefing on August 26, 2008, whether NIST had tested “any WTC 7 debris for explosive or incendiary chemical residues,” NIST lead investigator Dr. Shyam Sunder replied:

John Gross, who represented NIST on the FEMA Building Performance Study, poses next to the eroded, sulfidated steel. NIST would later claim that no identifiable steel was recovered from WTC 7, and John Gross would deny the existence of molten metal.

“[T]here is reference often made to a piece of steel from Building 7.... But that piece of steel has been subsequently analyzed by Professor Barnett and by Professor Rick Sisson, who is also from [WPI]...and they reported in a BBC interview that aired on July 6 [2008] that there was no evidence that any residue in that...piece of steel had any relationship to an...incendiary device in the building.” 6

Besides contradicting NIST’s position that no identifiable steel was recovered from WTC 7, Dr. Sunder’s response raises the question: Why did NIST not ask to study that piece of steel if they knew it existed? Furthermore, why did NIST not perform experiments to verify the leading fire-based explanation for the source of sulfur, which was the buildings’ gypsum wallboard?

Though NIST was not up to the task, a civil engineer named Jonathan Cole was. In his experiment documented in the video 9/11 Experiments: The Mysterious Eutectic Steel, he used a wide flange beam packed with crushed gypsum board, crushed concrete, aluminum scraps, steel scraps, and diesel fuel, and he burned it for 24 hours, continually adding fuel such as brush, furniture, floor panels, and wood logs. At the end of his experiment he reported:

“The aluminum, concrete, drywall, diesel fuel, and building materials did not cause any intergranular melting. So, if [these materials] did not cause the intergranular melting and sulfidation, then some uncommon substance that is not normally found in buildings must have caused it....

“There is a reason why NIST...never conducted any experiments or found that source of sulfur in order to solve this deepest of mysteries. Perhaps NIST knew the most logical cause of the sulfidation of the steel is from some type of thermitic reaction....”


Endnotes

[1] Glanz, James and Lipton, Eric: “A Search for Clues in the Towers’ Collapse,” The New York Times (February 2, 2002).

[2] Killough-Miller, Joan: “The Deep Mystery of Melted Steel,” WPI Transformations (Spring 2002).

[3] FEMA: World Trade Center Building Performance Study: Data Collection, Preliminary Observations, and Recommendations (May 2002), Appendix C, p. C-13.

[4] Jones, Steven: “Revisiting 9/11/2001 — Applying the Scientific Method,” Journal of 9/11 Studies (May 2007).

[5] NIST: Questions and Answers about the NIST WTC 7 Investigation, Question #27.

[6] NIST: WTC 7 Technical Briefing (August 26, 2008).

About an hour after the destruction of WTC 1 at 10:28 AM, the authorities at the World Trade Center began anticipating the collapse of WTC 7 with a high degree of confidence and precision. Their anticipation was so strong that the media widely reported on WTC 7’s imminent collapse, with some news outlets even reporting the collapse before it occurred.

A selection of the accounts illustrating this widespread anticipation is presented in Appendix B of Beyond Misinformation: What Science Says About the Destruction of World Trade Center Buildings 1, 2, and 7.

The official hypothesis would have us believe that the authorities’ anticipation was “evidence-based,” a prediction made on the basis of assessing the damage and fires in WTC 7. However, when examined closely, the high degree of confidence and precision suggests that it was instead knowledge-based. In other words, someone at the scene had foreknowledge that WTC 7 was going to be brought down and began warning others in order to avoid casualties and to create the cover story of a fire-induced failure. Thus, the warnings were couched as an evidence-based prediction that the building would collapse due to structural damage and fire.

The view that the anticipation was knowledge-based rather than evidence-based is strongly supported by the following facts:

  • NIST’s “Probable Collapse Sequence” for WTC 7 consists of an unprecedented and undetectable series of structural failures that could not be predicted on the basis of observing structural damage (which NIST later claimed did not contribute to the collapse) and fires. If we assume NIST’s hypothesis to be true, there would be no reason to anticipate a total collapse, even within the seconds before it occurred. Based on NIST’s scenario, the event that the authorities predicted had an infinitesimal probability of occurring until just seconds before it did. At that point, an extremely improbable chain of events unfolded and made their prediction correct. Such a scenario is not plausible.

Foreknowledge 1 AForeknowledge 1 B 

  • A number of buildings in the vicinity were on fire and sustained much greater damage from the destruction of WTC 1 and WTC 2. Yet authorities seized on WTC 7 as the one building that was certain to go down and established a safety zone around it.
  • The FEMA Building Performance Study concluded that the best hypothesis it could come up with had “only a low probability of occurrence.” 1 How were the authorities able to predict such a low-probability event?
  • Engineers were “stunned by what happened to 7 World Trade Center” and unable to explain it.2 Even as late as March 2006, NIST’s lead investigator told New York Magazine, “I don’t really know. We’ve had trouble getting a handle on building No. 7.” 3 How were the authorities able to predict an event that engineers would be unable to explain even four and half years later?
  • A CNN video captured both the sound of an explosion coming from WTC 7 and an emergency worker’s warning that WTC 7 was “about to blow up” just seconds before its destruction:

[Sound of explosion]. Unidentified voice: “You hear that?” Voice of emergency worker #1: “Keep your eye on that building, it’ll be coming down....” Voice of emergency worker #2: “Building is about to blow up, move it back.... Here we are looking back, there’s a building about to blow up. Flame and debris coming down.” 4


Endnotes

[1] FEMA: World Trade Center Building Performance Study: Data Collection, Preliminary Observations, and Recommendations (May 2002), Chapter 5, p. 5-31.

[2] Glanz, James: “Engineers Have a Culprit in the Strange Collapse of 7 World Trade Center: Diesel Fuel,” The New York Times (November 29, 2001).

[3] Jacobson, Mark: “The Ground Zero Grassy Knoll,” New York Magazine (March 2006).

[4] https://youtu.be/cU_43SwWD9A 

The seven-year quest to produce an official technical explanation for the destruction of World Trade Center Buildings 1, 2, and 7 represents an unparalleled case study in “expectation bias."

NFPA 921: Guide for Fire and Explosion Investigations, which serves as the national guide for fire and explosion investigations in the United States, defines “expectation bias” as follows:

“Expectation bias is a well-established phenomenon that occurs in scientific analysis when investigator(s) reach a premature conclusion without having examined or considered all of the relevant data. Instead of collecting and examining all of the data in a logical and unbiased manner to reach a scientifically reliable conclusion, the investigator(s) uses the premature determination to dictate investigative processes, analyses, and, ultimately, conclusions, in a way that is not scientifically valid. The introduction of expectation bias into the investigation results in the use of only that data that supports this previously formed conclusion and often results in the misinterpretation and/or the discarding of data that does not support the original opinion. Investigators are strongly cautioned to avoid expectation bias through proper use of the scientific method.”

NFPA 921 also explicitly urges investigators to avoid presumption in the formulation of hypotheses:

“Until data have been collected, no specific hypothesis can be reasonably formed or tested. All investigations of fire and explosion incidents should be approached by the investigator without presumption…until the use of scientific method has yielded testable hypotheses, which cannot be disproved by rigorous testing.”

As discussed below, the two official investigations of the WTC destruction flagrantly violated these principles, resulting in incomplete hypotheses that are wholly unsupported by any evidence and that ignore most of the relevant evidence.

The WTC FEMA Building Performance Study

Although investigators claimed that they were certain as to the cause of the Twin Towers’ destruction one week after the event — “Already there is near-consensus as to the sequence of events that led to the collapse of the World Trade Center,” R. Shankar Nair told the Chicago Tribune on September 19 — they were reportedly at a loss to explain the destruction of WTC 7.

“Engineers and other experts, who quickly came to understand how hurtling airplanes and jet fuel had helped bring down the main towers, were for weeks still stunned by what happened to 7 World Trade Center,” The New York Times reported on November 29. “We know what happened at 1 and 2, but why did 7 come down?” said William Baker, who was a member of the team assembled by the American Society of Civil Engineers (ASCE) and given authority under FEMA to investigate the World Trade Center destruction. 

Six months later, on May 1, 2002, FEMA released its report, titled World Trade Center Building Performance Study: Data Collection, Preliminary Observations, and Recommendations. As implied in the title, the report did not attempt to provide a definitive explanation for the destruction of WTC 7 (nor for WTC 1 and WTC 2). Instead, it posited scenarios in general terms and recommended further investigation to definitively determine the exact causes.

Regarding WTC 7, FEMA reported that there was “no clear evidence of where or on which floor the initiating failure occurred,” but it put forward a number of “potential scenarios” involving fires on various floors on the east side of the building. Noting that those areas contained “little if any fuel” that would be required to feed fires hot enough and long-lasting enough to weaken the structure, the report suggested “a hypothesis based on potential rather than demonstrated fact” that diesel fuel from the building's emergency generators was the source of fire. Like the “pancake theory” for WTC 1 and WTC 2, the diesel fuel hypothesis reflected common thinking at the time but was later ruled out by the National Institute of Standards and Technology (NIST). [Emphasis added.]

Then, toward the end of the report, FEMA observed:

“The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time. Although the total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence.” [Emphasis added.]

Thus, instead of pursuing the most likely hypothesis for WTC 7’s destruction — given that no steel-framed high-rise had ever collapsed due to fire and that the destruction of WTC 7 resembled a classic controlled demolition — FEMA posited a hypothesis that involved an unprecedented cause, for which it found no supporting evidence, and that it acknowledged had “only a low probability of occurrence.”

The NIST Investigation

Amid a growing sense that the FEMA investigation was insufficient for the task of conducting a full-scale investigation, NIST began planning its own investigation in October 2001 to eventually succeed FEMA’s. The NIST investigation was announced on August 21, 2002, and was scheduled to take 24 months.

In its final plan, released in August 2002, NIST acknowledged that fire had never caused the total collapse of a high-rise building prior to September 11, 2001. Nonetheless, it pursued this hypothesis without reservation, even going so far as to treat it as fact: “The WTC Towers and WTC 7 are the only known cases of total structural collapse in high-rise buildings where fire played a role.”

After releasing progress reports in December 2002 and May 2003 that provided little detail on its WTC 7 analysis, NIST finally announced a working hypothesis for WTC 7 in its June 2004 progress report. NIST suggested that an initial local failure somewhere below Floor 13, caused by fire and/or structural damage, triggered a column failure and subsequent vertical progression of failures up to the east penthouse. The resulting damage, NIST hypothesized, set off a horizontal progression of failures across the lower floors, resulting in disproportionate collapse of the entire building.

NIST’s working hypothesis for the destruction of WTC 7 was further elaborated in a Popular Mechanics article from March 2005, which said: “NIST researchers now support the working hypothesis that WTC 7 was far more compromised by debris than the FEMA report indicated.... NIST investigators believe a combination of intense fire and severe structural damage contributed to the collapse.”

In its April 2005 progress report, NIST announced for the first time that its report on WTC 7 would be released as a supplement to its report on WTC 1 and WTC 2, with a draft report scheduled for October 2005 and the final report slated for December 2005. Notably, NIST addressed the subject of the controlled demolition hypothesis for the first time — but only in relation to WTC 7: “NIST has seen no evidence that the collapse of WTC 7 was caused by bombs, missiles, or controlled demolition.” NIST did not describe what methods it used to search for evidence of controlled demolition.

Then, in September 2005, at a three-day technical conference where NIST released its final report on WTC 1 and WTC 2, it announced that its report on WTC 7 would be further postponed, with the technical work being completed in January 2006, the draft report for public comment scheduled for May 2006, and the final report finished in June 2006.

But NIST ended up significantly extending that timeline. A report that in June 2005 was set for release by the end of that year would end up being released almost three years later. In a March 2006 New York Magazine interview, NIST lead investigator Dr. Shyam Sunder provided some possible insight into why the report was delayed so long. When asked about WTC 7, Dr. Sunder said that NIST had some “preliminary hypotheses,” then added, “But truthfully, I don’t really know. We’ve had trouble getting a handle on building No. 7.” This was three and a half years into NIST’s WTC investigation.

That same month, NIST awarded a new contract to Applied Research Associates for the job of determining the location and cause of the initiating event and the subsequent series of failures that led to the total collapse of WTC 7. The contract was appended in August 2006 to include the task of determining if any “hypothetical blast event or events” contributed to the destruction of WTC 7.

In August 2008, the draft for public comment was finally released. That November, the final report was published. Diesel fuel fires and structural damage were no longer hypothesized to have contributed to the collapse. Instead, normal office fires were said to be the sole cause, making it “the first known instance of the total collapse of a tall building primarily due to fires.”

As researcher Frank Legge said of WTC 1 and WTC 2 two months before the release of NIST’s draft report on WTC 7, “the fire based official explanation is a series of events, like links in a chain, while the explosive based explanation is a parallel set of scientific studies of evidence…. If an explanation is in the form of a chain it is only necessary to prove one link wrong to destroy the case.” The same can be said of NIST's explanation for the destruction of WTC 7, except that the chain of events alleged by NIST is even more elaborate. The table below is a summary of NIST’s “Probable Collapse Sequence” for WTC 7.

A summary of NIST’s “Probable Collapse Sequence” for WTC 7.

Below we focus on NIST’s superficial attempt to rule out the use of explosives in the destruction of WTC 7 and on the most glaring issues in NIST’s modeling of WTC 7.

For discussion of NIST’s failure to explain WTC 7’s free fall, see Free-Fall Acceleration. For more extensive critiques of NIST’s explanation for the destruction of WTC 7, see the items under “More on this Subject.”

Hypothetical Blast Scenarios and Thermite Use

The only substantive analysis that NIST performed regarding the hypothesis of controlled demolition was its consideration of “hypothetical blast scenarios” for the destruction of WTC 7, carried out under a contract with Applied Research Associates beginning in August 2006.

NIST’s analysis started with identifying a hypothetical blast event involving the minimum amount of explosive material required to fail Column 79. It determined that to be a linear-shaped charge consisting of nine pounds of RDX. From there, it performed analyses to assess how much window breakage and noise would result — and whether it was feasible for someone to plant such explosives in the building.

NIST concluded the following:

  • [T]he minimum charge (lower bound) required to fail a critical column (i.e., Column 79) would have produced a pressure wave that would have broken windows on the north and east faces of the building near Column 79. The visual evidence did not show such breakage....
  • [T]he noise level at a distance of 1/2 mile would have been on the order of 130 dB to 140dB.... People on the street would have heard 9 lb of RDX go off a mile away....
  • Preparations for a blast scenario would have been almost impossible to carry out on any floor in the building without detection....2

NIST’s analysis of “hypothetical blast scenarios” is a textbook example of straw man tactics, where an argument is constructed and then refuted to give the impression that an opponent’s argument has been defeated, when in fact the refuted argument is not the opponent’s.

Proponents of the controlled demolition hypothesis have seldom, if ever, argued that a high explosive such as RDX was used to destroy WTC 7. Rather, as the evidence examined in High-Temperature Thermitic Reactions and Steel Sulfidation strongly suggests, the leading hypothesis is that an explosive form of thermite called “nano-thermite” — possibly in combination with some form of explosives and other incendiaries — was used to destroy WTC 7. Using nano-thermite, instead of the more powerful RDX, would allow a perpetrator to demolish a building while concealing the fact that he had planted explosives.

Even though NIST was fully aware of nano-thermite technology3 and it knew that the leading hypothesis of controlled demolition involved some form of thermite, as evidenced by its FAQ (see below), it selected a “straw man” substance — RDX — for its hypothetical blast event. Thus, its analyses of the window breakage and noise associated with RDX are irrelevant.

Furthermore, the evidence examined in Explosions contradicts NIST’s claim that explosions were not observed by eyewitnesses or captured on video. Indeed, explosions were observed by eyewitnesses and captured on video. As one person at the scene recounted, “[I]t looked like there was a shockwave ripping through the building and the windows all busted out.”

In suggesting that “[o]ccupants, support staff, and visitors would have noticed evidence of such activities [i.e., placing charges],” NIST also assumed that the planting of explosives would have happened without the knowledge of someone responsible for security at WTC 7. But proponents of the controlled demolition hypothesis have seldom suggested that the planting of explosives could have been accomplished without the knowledge and complicity of someone in charge of security at WTC 7.

NIST’s analysis also assumed that a demolition of WTC 7 would have been executed in the manner of a typical commercial controlled demolition. But according to researcher Jim Hoffman, “[E]xplosive devices could have been disguised as or concealed within legitimate equipment.... Numerous such possibilities are afforded by the properties of energetic materials.” In fact, Hoffman argues, “Any such job would have been far simpler than the structural retrofit of the CitiCorp Tower” — a feat the owners successfully managed in 1978 without their tenants knowing about it, after learning that the building was likely to topple in a hurricane.4

Thermite Instead of Nano-Thermite

NIST advanced a second straw man argument when it tackled the idea in both of its FAQ documents (one for the Twin Towers, the other for WTC 7) that thermite or thermate alone was used to destroy the buildings. NIST gave the following answer in response to the question of whether it tested the steel for residues of thermite:

“[Thermite] burns slowly relative to explosive materials.... 0.13 pounds of thermite would be required to heat each pound of a steel section to approximately 700 degrees Celsius.... [M]any thousands of pounds of thermite would need to have been placed inconspicuously ahead of time.... This makes it an unlikely substance for achieving a controlled demolition.” 5

Once again, NIST constructed an easily refutable argument that is not the argument actually advanced by proponents of the controlled demolition hypothesis. It is well known that thermite and thermate alone do not possess the explosiveness needed to account for a large amount of the evidence of explosions that NIST itself ignored.

Had it been NIST’s genuine intention “to determine whether explosives could have been used to cause the collapse[s],” it would have tested the steel for explosives and thermite residues.

NIST's Computer Modeling

Because most of the WTC steel was destroyed before it could be inspected, the NIST WTC investigation had to rely almost entirely on computer modeling. The modeling performed by NIST failed — effectively disproving its hypothesis — in two ways:

1. It did not replicate the observed structural behavior of the buildings, and

2. It required significant manipulation — in other words, applying information known to be factually unsupported — in order to achieve collapse initiation.

As discussed in Free-Fall Acceleration, NIST asserted that the three stages of collapse progression it measured for WTC 7 were “consistent with the results of the global collapse analyses discussed in Chapter 12 of NIST NCSTAR 1-9” (where NIST presented the results of its computer model).

However, when we view the model,6 we see — besides the fact that it stops after only two seconds, which is well before the end of the collapse — that it fails to replicate the observed structural behavior in two important ways. First, it fails to show the 2.25 seconds of free fall that NIST finally acknowledged. Second, it shows large deformations of the building’s exterior structure that are not observed in the videos.

This illustration from the NIST report shows the mechanism that NIST claims initiated the collapse of WTC 7: Floor beams (green) thermally expanded and pushed girder A2001 (blue) off of the seat connecting it to Column 79 (purple).

NIST also had to manipulate its modeling significantly just to get the collapse to initiate. Specifically — in order to make the floor beams under Floor 13 expand and push the critical girder (A2001) off its seat and allegedly trigger a total collapse of the building — NIST took the following steps:

1. It ignored the fact that the fire in the northeast section of Floor 12 had burned out over an hour before it supposedly caused the beams under Floor 13 to expand.

2. It omitted shear studs on girder A2001 that would have prevented the girder from being pushed off its seat.

3. It inexplicably heated the floor beams but not the floor slab above them, thus causing the floor beams, but not the slab, to expand. This caused the shear studs connecting the floor beams and the slab to fail, which allowed the floor beams to move independently of the slab.

4. It ignored the fact that the floor beams could expand no more than 5 3/4 inches — less than the 6 1/4 inches required to push the girder off its seat — before shortening, caused by sagging, would overtake expansion.

5. It omitted web/flange stiffeners that would have prevented the bottom flange of the girder from folding (even if the beams had somehow expanded 6 1/4 inches).

Had NIST modeled WTC 7 accurately, the mechanism that it claimed initiated the collapse would not have been feasible.


Endnotes

[1] Legge, Frank: “9/11 and Probability Theory,” Journal of 9/11 Studies (June 2008).

[2] NIST: NCSTAR 1-9, p. 357.

[3] Ryan, Kevin: “The Top Ten Connections Between NIST and Nano-Thermites,” Journal of 9/11 Studies (July 2008).

[4] Hoffman, Jim: "Frequently Asked Questions: Controlled Demolition," 9-11Research.WTC7.nethttp://911research.wtc7.net/faq/demolition.html.

[5] NIST: Questions and Answers about the NIST WTC Towers Investigation, Question #22.

[6] http://wtcdata.nist.gov/gallery2/v/NIST+Materials+and+Data/Computer+Simulations/WTC7_Structural+Response

[7] NIST public affairs officer Michael Newman confirmed in email correspondence with researcher David Cole on October 25, 2013, that the web/flange stiffeners on girder A2001 were omitted from NIST’s computer model of WTC 7.